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Fluvial systems are particularly sensitive to changes in the terrestrial ecosystems where they are embedded, receiving simultaneously the impact of multiple stressors. The design of adequate management policies requires analyzing fluvial systems as social-ecological systems, because the decoupling of natural and social systems can lead to a severe mismatch between maintaining ecological integrity and the pursuit of human well-being. Pampean streams are especially prone to the impact of human activities because they are located in a region that provides almost half of the agricultural production of Argentina and concentrates 66% of the whole population of the country. In the present work, we conceived a general social-ecological framework that links the occurrence of multiple stressors and their impacts on ecosystem services, with changes in environmental perception of streams, which in turn feedback over institutional actions at the watershed's governance. We identified four current key drivers of the dynamics in Pampean streams: a dominant agro-industrial model for the region, a command-and-control governance regime mainly based on an engineering hydraulic perspective, the real estate market speculation of surrounding lands, and the persistence of structural poverty in urban areas. The resulting dynamics resembles the occurrence of different kinds of social-ecological traps, i.e., a highly stable but undesirable state of the system that is difficult to escape. Based on this analysis, we provide a leverage point perspective to avoid this trap. Together, this approach could be applied to other fluvial systems of the world to link the ecological and social domains to multiple stressors analysis, and to improve institutional fit for the sustainability of fluvial social-ecological systems.

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In this study, we evaluated the distribution of up to forty-three antibiotics and 4 metabolites residues in different environmental compartments of an urban river receiving both diffuse and point sources of pollution. This is the first study to assess the fate of different antibiotic families in water, biofilms and sediments simultaneously under a real urban river scenario. Solid phase extraction, bead-beating disruption and pressurized liquid extraction were applied for sample preparation of water, biofilm and sediment respectively, followed by the quantification of target antibiotics by UPLC-ESI-MS/MS. Twelve antibiotics belonging to eight chemical families were detected in Suquía River samples (67% positive samples). Sites downstream the WWTP discharge were the most polluted ones. Concentrations of positive samples ranged 0.003-0.29 µg L-1 in water (max. cephalexin), 2-652 µg kg-1d.w. in biofilm (max. ciprofloxacin) and 2-34 µg kg-1d.w. in sediment (max. ofloxacin). Fluoroquinolones, macrolides and trimethoprim were the most frequently detected antibiotics in the three compartments. However cephalexin was the prevalent antibiotic in water. Antibiotics exhibited preference for their accumulation from water into biofilms rather than in sediments (bioaccumulation factors > 1,000 L kg-1d.w. in biofilms, while pseudo-partition coefficients in sediments < 1,000 L kg-1d.w.). Downstream the WWTP there was an association of antibiotics levels in biofilms with ash-free dry weight, opposite to chlorophyll-a (indicative of heterotrophic communities). Cephalexin and clarithromycin in river water were found to pose high risk for the aquatic ecosystem, while ciprofloxacin presented high risk for development of antimicrobial resistance. This study contributes to the understanding of the fate and distribution of antibiotic pollution in urban rivers, reveals biofilm accumulation as an important environmental fate, and calls for attention to government authorities to manage identified highly risk antibiotics.

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The aim of this study was to test whether the water quality phytoplankton assemblage index adapted for rivers (Qr index) is useful to characterize the water quality of a neotropical stream. We were interested also in inferring the main pollutants through a phytoplankton functional trait characterization and assessing the phytoplankton groups which may influence the Qr index final estimations. Monthly sampling of environmental variables and phytoplankton were done in three sites (S1, S2, and S3). Phytoplankton was classified according to Reynolds Functional Groups (RFG) and water quality estimation was performed using the Qr index. Principal coordinates (PCO) and PERMANOVA were applied to identify the main pollutants through the RFG. RFG linkage to Qr values was assessed by general linear models (GLM). "Moderate" water quality was found in S1 the whole year, in all sampling stations during the winter, and in summer-autumn in S2. "Regular" water quality was found in S3 during the summer-autumn, and S2-S3 during the spring. S1 and S2 showed eutrophic, standing, or mix waters whereas S3 had high organic matter content and eutrophic conditions. Despite some RFG (X1 and MP) being linked to high Qr values and some other (M, S1 and Z) to low, their dominance did not influence water quality estimation performed by the Qr. We conclude that the Qr index was useful for assessing the water quality. Though RFG were valuable for inferring eutrophication, organic pollution, and mixing, but their dominance does not necessarily have a direct effect on the final Qr estimation.

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The lower portion of the Reconquista River is highly polluted. However, little is known about the state of the high and middle basins. The aims of this work were to assess the water quality on the high and middle Reconquista River basins and to determinate if the presence of a reservoir in the river has a positive effect on the water quality. We conducted a seasonal study between August 2009 and November 2010 at the mouth of La Choza, Durazno, and La Horqueta streams at the Roggero reservoir--which receives the water from the former streams--at the origin of the Reconquista River and 17 km downstream from the reservoir. We measured 25 physical and chemical parameters, including six heavy metal concentrations, and performed a multivariate statistical analysis to summarize the information and allow the interpretation of the whole data set. We found that the Durazno and La Horqueta streams had better water quality than La Choza, and the presence of the reservoir contributed to the improvement of the water quality, allowing oxygenation of the water body and processing of organic matter and ammonia. The water quality of the Reconquista River at its origin is good and similar to the reservoir, but a few kilometers downstream, the water quality declines as a consequence of the presence of industries and human settlements. Therefore, the Roggero reservoir produces a significant improvement of water quality of the river, but the discharge of contaminants downstream quickly reverses this effect.

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We analyzed the relationship between biodiversity and spatial biomass heterogeneity along an ecological succession developed in the laboratory. Periphyton (attached microalgae) biomass spatial patterns at several successional stages were obtained using digital image analysis and at the same time we estimated the species composition and abundance. We show that the spatial pattern was self-similar and as the community developed in an homogeneous environment the pattern is self-organized. To characterize it we estimated the multifractal spectrum of generalized dimensions D(q). Using D(q) we analyze the existence of cycles of heterogeneity during succession and the use of the information dimension D(1) as an index of successional stage. We did not find cycles but the values of D(1) showed an increasing trend as the succession developed and the biomass was higher. D(1) was also negatively correlated with Shannon's diversity. Several studies have found this relationship in different ecosystems but here we prove that the community self-organizes and generates its own spatial heterogeneity influencing diversity. If this is confirmed with more experimental and theoretical evidence D(1) could be used as an index, easily calculated from remote sensing data, to detect high or low diversity areas.

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The aim of this research was to study the effects on streams water quality of non-point contamination as agriculture and cattle farming activities at a basin with pampean characteristics located at the upper Reconquista River Basin. Eight reaches with different uses in their neighboring zones were selected with the proposed to detect differences at the water quality among them. SRP range was 0-0.60 mgP.PO (4) (-3) /L, ammonia 1-137.3 µgN-NH4(+)/L and nitrate 0-4.15 mgN-NO(3) (-)/L. There was high similitude and homogeneous physicochemical characteristics at the different reaches of the streams. The high levels of dissolved nutrients showed similar eutrophication conditions at the streams.

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Seasonal sampling was carried out at four sites on a pampean stream that receives industrial effluent from two textile factories. To evaluate water quality, several physical and chemical parameters were examined and the periphyton growing on cattail (Typha latifolia L.) were analyzed. Water quality and periphyton structure differed significantly between sites upstream and downstream of the discharge. Differences in temperature and also in concentrations of phosphate, dissolved oxygen, and phaeopigment were detected. At the same time, changes in the dominant algae groups were observed. Downstream of the industrial discharge, the number of Bacillariophyta decreased, while species of Cianophyta and Euglenophyta were more abundant. This abundance correlated with increased phosphate and organic matter content and decreased oxygen concentration. Although this study did not detect a reduction in the number of species, similarity between stands decreased downstream of the industrial discharge. Changes in community structure were readily detected in this situation because the communities of the polluted and unpolluted zones were qualitatively different. Periphyton growing naturally on Typha latifolia is a useful indicator of the impact of waste waters on the biota and can also be used to evaluate water body recovery.

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El objetivo de este trabajo es caracterizar a los arroyos de la cuenca del Río Lujan en base a sus variables físicos-químicas, biológicas y microbiológicas antes de atravesar focos contaminantes

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El objetivo de este trabajo es caracterizar a los arroyos de la cuenca del Río Lujan en base a sus variables físicos-químicas, biológicas y microbiológicas antes de atravesar focos contaminantes

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